The doctor said jokingly that his own infection of the virus _______ the discovery of a vaccine (疫苗)of the disease.
When I was young, I was told that I ______ play with matches
-What sort of house do you want to have? Something big?--Well, it ______ be big--that's not important.
—I can’t find my purse anywhere.—You __ have lost it while shopping.
Although this ____ sound like a simple task, great care is needed.
Liza ___ well not want to go on the trip --- she hates traveling.